Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed world), yet the description still adds real value: authentication scope (full_access key), result ordering (newest first), and payload shape (bodies omitted). Rate limits or a total-count/next-page-flag note would be the only remaining gaps.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded one-sentence summary followed by a tight behavior line and a prerequisite line; nothing is buried. The trailing 'API: GET /emails (operationId listEmails, Emails)' line is reference metadata that adds little for an agent choosing a tool.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a read-only list tool with no output schema and a fully documented schema, the description covers ordering, payload exclusions, and auth. Only pagination mechanics (how to obtain the cursor ids in practice) are left implicit.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and the schema already documents before/after mutual exclusion and the 1–100 limit range, so the description can legitimately defer. It adds nothing parameter-specific (e.g., that cursors are opaque ids from a prior response), so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('List emails') and immediately narrows scope: sent and scheduled emails, newest first, bodies excluded. That scope detail separates it implicitly from get_email, though the sibling is never named.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The prerequisite ('Requires a `full_access` API key') is useful routing context, and the 'no bodies' note hints at when to reach for get_email instead. But no alternative is named and no exclusion or when-not condition is given.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.